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Chapter 4. Discussion
This evidence report summarized, critically appraised, and compared the evidence on
clinical benefits and harms associated with the administration of different types of
pharmaceutical agents in the treatment of erectile dysfunction (ED).
Strength of the Evidence
Erectile dysfunction is a complex condition related to psychosocial and biological factors.
It is difficult to reliably document and measure the degree of treatment success in patients
diagnosed with this condition. Most of the validated and clinically relevant efficacy
outcomes assessed in clinical trials of ED patients are subjective.
The strength of evidence regarding the utility of routine endocrinological blood tests
found in this review was limited in terms of the both amount and quality of data. The studies
were heterogeneous with respect to patient population characteristics, diagnostic methods,
estimates of prevalence, and laboratory methods used (e.g. cut-off values, total, free, or
bioavailable hormonal levels).
The placebo-controlled randomized trials that evaluated the efficacy and harms of PDE–5
inhibitors provided large amount of evidence and consistently indicated that patients who
received PDE–5 inhibitors experienced greater improvements in erectile dysfunction
compared with placebo-treated patients. The magnitude of benefit was clinically relevant and
statistically significant. The methodological and reporting quality of the evidence provided
by these trials was better than that for other studies (e.g. trials with active control arms or
trials evaluating sublingual apomorphine, injections, topical, hormonal, or off-label
therapies). Most of these trials enrolled ED patient populations with a broad spectrum of
etiologies or comorbidities and assessed the same set of clinically relevant and validated
outcome measures. Given the reported exclusion criteria for these trials, their results may not
be readily applicable to ED patients with major chronic disorders (e.g. cancer, CVD,
diabetes, psychiatric disorders, hepatic or renal diseases) or post-surgery patients, because the
magnitude of clinical benefit conferred by PDE-5 inhibitors in such patients is relatively
modest. 384-386 Furthermore, vardenafil trials may have been comprised of more responsive
patients due to the fact that about half of these trials excluded patients refractory to prior
sildenafil therapy, thereby limiting the applicability of the results to a broader population of
ED patients. On average, trials that evaluated injected (e.g. intracavernosal, subcutaneous),
intra-urethral, topical, or other treatments were of relatively lower methodological and
reporting quality.
A common limitation of these trials was a failure to assess and/or report clinically
relevant treatment efficacy outcomes used for the measurement of the degree of erectile
dysfunction (e.g. mean scores for International Index of Erectile Function, Sexual Encounter
Profile, Global Assessment Question regarding improved erection). The most commonly
assessed efficacy outcomes in these trials were penile rigidity (using RigiScan) and the
quality of erections achieved at home. The trials did not report information on the methods
used for randomization, blinding, and allocation concealment. Many study results may have
been biased in favor of active treatment, because the analyzed samples predominantly
included responders and excluded many randomized participants from their efficacy
analyses. There was substantial heterogeneity across the hormonal treatment trials with
respect to the diversity of patient populations (variations in inclusion/exclusion criteria; not
Appendixes and Evidence Tables for this report are provided electronically at
http://www.ahrq.gov/downloads/pub/evidence/pdf/erectiledys/erecdys.pdf